5 ms·

That would be very useful. We sadly stopped innovating on optical media, but haven't really made the alternatives usable as a replacement. You used to have CDs

That would be very useful. We sadly stopped innovating on optical media, but haven't really made the alternatives usable as a replacement. You used to have CDs / DVDs that were: 1. Completely immutable 2. Could not be maliciously altered by the reader 3. Could not masquerade as a keyboard or a mouse

ace2358 3y ago
I miss physical media, optical or magnetic. Or something new!! Flash drivers are just computers these days.
- simbolit 3y ago
  In what sense is a nand chip, a memory controller, and a usb plug, a "computer these days"?
  - toast0 3y ago
    The flash memory controller is most likely a embedded stored program computer. Likely an arm, maybe dual core. A modern computer is really a distributed system, but not a lot of people frame the discussion that way.
  - yencabulator 3y ago
    https://www.bunniestudios.com/blog/?page_id=3592 https://www.bunniestudios.com/blog/?page_id=3592 > The embedded microcontroller is typically a heavily modified 8051 or ARM CPU. In modern implementations, the microcontroller will approach 100 MHz performance levels, and also have several hardware accelerators on-die.
Syonyk 3y ago
You still do. I can't be the only person who burns install DVDs, finalized, verifies the hash on a few different systems, and then keeps them in a safe place for possible future use... I've got some external USB readers/burners that excel for exactly this sort of thing, and just about anything that will run a modern OS will boot from them.
- JohnFen 3y ago
  You're not the only one. I still do this, and use CDs/DVDs for all sorts of other longer-term storage as well. I'm unaware of any other media that works well for those sorts of use cases.
  - superb_dev 3y ago
    What is the shelf life of a modern CD/DVD? I might consider using them more
    - JohnFen 3y ago
      At room temperature, about 25 years -- but there are a lot of variables that can affect this in both directions. https://www.clir.org/pubs/reports/pub121/sec4/ https://www.clir.org/pubs/reports/pub121/sec4/
      - dml2135 3y ago
        Maybe for commercial-grade optical media, but last time I burned a lot of consumer media , I found a decent amount of failures even just a few years out. Admittedly this was almost 20 years ago at this point so maybe some things have improved since then but my understanding is that consumer media uses a different, ink-based technology to write data to disk, and that ink can degrade pretty quickly. This is in contrast to commercial optical media in which the data is stamped into the disk in a manner more akin to a vinyl record.
        JohnFen 3y ago
        All CD-Rs use a dye layer, yes. The life expectancy the link I provided is talking about is for writeable media, not for read-only media that is stamped. Some forms of writeable disc media don't use dyes and can last for over 100 years. Check out the link. But, to your point, one of the variables that affect longevity is the quality of the manufacturing. If you're buying the least expensive media you can find, then the lifespan is indeed shorter. For my cheapo CD-Rs, I've found that they last 5-10 years. You can also make them last longer by storing them in better conditions (vertically, not laying flat, in an airtight container in the freezer). I tend to go with cheap media, so my personal habit is to burn new copies of my storage discs every 5 years.
mike_hock 3y ago
> Completely immutable Wouldn't the laser of a CD/DVD writer be powerful enough to alter the data after the fact? Not to overwrite it with completely arbitrary data, but flipping a few well-chosen bits should in principle be able to create a backdoor that wasn't there before (if it's a live or install disk, for example).
- JohnFen 3y ago
  You can change things, yes, but not in a way that keeps the disc usable. The issue here is that you can't "unburn" a bit that has been burned. Since you burn 0s, not 1s, all you can do is make more bits 0 -- which would then be corrected by the error correction mechanism. You could alter the EC codes, but that would render them useless and eliminate the ability to correct errors, causing the data to be unreadable by a normal drive due to EC failure. So, in practice, they're pretty safe. The worst thing that an attacker could do is to render the media unusable.
  - calamari4065 3y ago
    That's not completely true either. I used to use some sketchy utility back in the day that could mark one recording session as inaccessible and let you add data to any remaining space on the disc. You would only see the new session. Hypothetically you can also manipulate the file table to make it look exactly like the real thing. I don't remember if it required the disc to be un-finalized or not. It probably did. But this is really an edge case
    - JohnFen 3y ago
      True, I was assuming the disc wasn't written as a multi-session one (most people never use multi-session). Multi-session discs are a bit different. But, afaik, if the disc has been finalized then the result is as "immutable" as a non-multisession one. I'm not completely certain about that, though.
  - mike_hock 3y ago
    Are the EC codes such that any alteration from 1 to 0 in the message results in at least one flip from 0 to 1 in the (correct) EC code? If not, then you "just" have to find the right spots where such a simultaneous alteration of the payload and the EC code is possible, and which also happens to result in a desirable behavior change.

ace2358 3y ago

I miss physical media, optical or magnetic. Or something new!! Flash drivers are just computers these days.

simbolit 3y ago
In what sense is a nand chip, a memory controller, and a usb plug, a "computer these days"?
- toast0 3y ago
  The flash memory controller is most likely a embedded stored program computer. Likely an arm, maybe dual core. A modern computer is really a distributed system, but not a lot of people frame the discussion that way.
- yencabulator 3y ago
  https://www.bunniestudios.com/blog/?page_id=3592 https://www.bunniestudios.com/blog/?page_id=3592 > The embedded microcontroller is typically a heavily modified 8051 or ARM CPU. In modern implementations, the microcontroller will approach 100 MHz performance levels, and also have several hardware accelerators on-die.

Syonyk 3y ago

You still do. I can't be the only person who burns install DVDs, finalized, verifies the hash on a few different systems, and then keeps them in a safe place for possible future use... I've got some external USB readers/burners that excel for exactly this sort of thing, and just about anything that will run a modern OS will boot from them.

JohnFen 3y ago
You're not the only one. I still do this, and use CDs/DVDs for all sorts of other longer-term storage as well. I'm unaware of any other media that works well for those sorts of use cases.
- superb_dev 3y ago
  What is the shelf life of a modern CD/DVD? I might consider using them more
  - JohnFen 3y ago
    At room temperature, about 25 years -- but there are a lot of variables that can affect this in both directions. https://www.clir.org/pubs/reports/pub121/sec4/ https://www.clir.org/pubs/reports/pub121/sec4/
    - dml2135 3y ago
      Maybe for commercial-grade optical media, but last time I burned a lot of consumer media , I found a decent amount of failures even just a few years out. Admittedly this was almost 20 years ago at this point so maybe some things have improved since then but my understanding is that consumer media uses a different, ink-based technology to write data to disk, and that ink can degrade pretty quickly. This is in contrast to commercial optical media in which the data is stamped into the disk in a manner more akin to a vinyl record.
      - JohnFen 3y ago
        All CD-Rs use a dye layer, yes. The life expectancy the link I provided is talking about is for writeable media, not for read-only media that is stamped. Some forms of writeable disc media don't use dyes and can last for over 100 years. Check out the link. But, to your point, one of the variables that affect longevity is the quality of the manufacturing. If you're buying the least expensive media you can find, then the lifespan is indeed shorter. For my cheapo CD-Rs, I've found that they last 5-10 years. You can also make them last longer by storing them in better conditions (vertically, not laying flat, in an airtight container in the freezer). I tend to go with cheap media, so my personal habit is to burn new copies of my storage discs every 5 years.

mike_hock 3y ago

> Completely immutable Wouldn't the laser of a CD/DVD writer be powerful enough to alter the data after the fact? Not to overwrite it with completely arbitrary data, but flipping a few well-chosen bits should in principle be able to create a backdoor that wasn't there before (if it's a live or install disk, for example).

JohnFen 3y ago
You can change things, yes, but not in a way that keeps the disc usable. The issue here is that you can't "unburn" a bit that has been burned. Since you burn 0s, not 1s, all you can do is make more bits 0 -- which would then be corrected by the error correction mechanism. You could alter the EC codes, but that would render them useless and eliminate the ability to correct errors, causing the data to be unreadable by a normal drive due to EC failure. So, in practice, they're pretty safe. The worst thing that an attacker could do is to render the media unusable.
- calamari4065 3y ago
  That's not completely true either. I used to use some sketchy utility back in the day that could mark one recording session as inaccessible and let you add data to any remaining space on the disc. You would only see the new session. Hypothetically you can also manipulate the file table to make it look exactly like the real thing. I don't remember if it required the disc to be un-finalized or not. It probably did. But this is really an edge case
  - JohnFen 3y ago
    True, I was assuming the disc wasn't written as a multi-session one (most people never use multi-session). Multi-session discs are a bit different. But, afaik, if the disc has been finalized then the result is as "immutable" as a non-multisession one. I'm not completely certain about that, though.
- mike_hock 3y ago
  Are the EC codes such that any alteration from 1 to 0 in the message results in at least one flip from 0 to 1 in the (correct) EC code? If not, then you "just" have to find the right spots where such a simultaneous alteration of the payload and the EC code is possible, and which also happens to result in a desirable behavior change.